Author: L. A. Helfrich, Extension Specialist, Fisheries Virginia Tech
Publication Number 420-019, Revised 1999
Introduction
At one time or another nearly every farm pond owner has been frustrated
by at least one of the many problems that affect ponds and pond life. Among
the 60,000 privately owned ponds scattered throughout Virginia, a large
number fail to hold water, contain muddy waters, are choked with waterweeds,
or do not produce good sportfish populations. This publication addresses
these and other typical problems that plague pond owners. Since most pond
problems can be avoided, we emphasize preventing problems through careful
planning, proper construction, correct stocking, and sound management.
Solutions to problems resulting from bad weather, unauthorized fish harvest,
accidental introductions of nuisance fish, and chemical contamination are
presented.
Selecting the Pond Site
Careful selection of the pond site is one of the most important steps
in avoiding farm pond problems. A good pond site contains (1) a topography
(“lay of the land”) that provides for economical pond construction; (2)
a water supply that provides adequate but not excessive, amounts of water;
and (3) a soil type with sufficient clay content to hold water. Failure
to select a good site will result in serious pond problems (flooding, leakage,
pollution) that are very expensive to correct. Before making the final
site selection, a pond owner should consider all potential sites and consult
with soil scientists and engineers. The Soil Conservation Service, with
agents in almost all counties in Virginia, will provide (free of charge)
soil testing and site selection advice to landowners.
Topography
The topography of the pond site should be carefully evaluated to minimize
costly soil removal. Ideally, the topography of the land should be relatively
flat, permitting construction of a pond of regular size, shape, and depth.
Optimal pond sites are located in small, stable, well-vegetated drainage
basins, preferably above the flood plain. Flooding causes serious problems
in managing sportfish ponds. Incorporating the topography of the land with
the design of the pond dam will permit natural drainage and avoid expensive
drain systems or costly pumping equipment.
Water Supply
A continuous supply of high-quality water should be available throughout
the year to replenish losses due to evaporation, seepage, or partial drainage
of the pond for irrigation, weed control, or fish management purposes.
The water supply should be sufficient to provide enough water to fill the
pond within a reasonable period of time (less than 15 days) and maintain
a relatively constant water level (fluctuations less than 2 feet year-round).
Excessive inflows flush essential nutrients downstream and may allow valuable
sportfish to escape.
Small streams are a major source of water for most Virginia ponds. These streams are satisfactory if (1) the flow is adequate to maintain a relatively constant water level; (2) the stream is not subject to heavy flooding; (3) the watershed is forested; and (4) the stream carries a light silt load. When a stream is used as a water supply, it should be directed around the pond and have an inlet pipe which can be screened and closed as needed. An inlet pipe with an open-close valve provides control over water level, siltation, and nuisance fish entry.
Springs, wells, and underground seepage provide additional sources of water for farm ponds. Water from these sources normally assures a reliable flow of high-quality water free of fish diseases, fish parasites, silt, nuisance fish, predators, pesticides, and other contaminants. Some ground waters, however, contain high levels of carbon dioxide, nitrogen, or minerals, which can be harmful to fish and other aquatic life. All waters should be analyzed before pond construction to assure that they can sustain aquatic life.
Surface runoff (waters which flow on the land surface after rains) is
another source of water for filling farm ponds. In Virginia, about 3 acres
of watershed land is required to provide for each 1 acre foot of pond water
(1 acre foot = 1 acre of water 1 foot deep). Thus, pond owners wishing
to provide sufficient water flow for a pond one surface acre in size and
6 feet deep (6 acre-feet) should have a watershed area of approximately
18 acres. The exact watershed area required to fill a pond and maintain
the water level year-round varies with land use and soil types. For example,
a larger watershed area may be necessary to fill ponds located on forested
watersheds or sandy soils than to fill those located on pasture lands or
in clay soils. Since surface water runoff may transport high quantities
of silt, nutrients, and pesticides, ponds fed only by surface waters are
subject to more problems than those fed by streams, springs, and wells.
A diversion ditch around a farm pond can be used to control runoff water
levels and prevent contaminated waters from entering the pond.
Bottom Soils
Since the pond is simply a container for holding water, its dam and
bottom must be composed of a soil that minimizes seepage. Soils with a
high clay content are preferred because clay particles tend to swell when
wet and, thereby, help to seal the pond bottom. It's impractical to build
a pond on soils that will not hold water. Sites located in gravel or sandy
soils are often too porous to seal effectively. Similarly, sites in limestone
or shale regions are frequently unsuitable because of the high risks of
fractures that create leaks. Sites in swampy areas may also be unsuitable
because they are often difficult to drain and costly to maintain.
Pond Construction
Inflow-Outflow Control
Ideally, the pond owner should have complete control of the water entering
and leaving the pond. Thus, two of the most important structural requirements
of a good farm pond are (1) a permanent drain, and (2) an inlet control
structure. Since it is often necessary to lower water levels to control
flooding, erosion, waterweeds, and fish populations, an “easily operated”
drain of “adequate size” (sufficient to drain the pond in 5 days or less)
is essential. Water levels in old ponds lacking a drain can be controlled
by pumping or siphoning, but these are time-consuming and expensive alternatives
that cannot substitute for an adequate drain. Similarly, since it is often
necessary to prevent waters containing chemical contaminants, heavy silt
loads, or nuisance fish from entering the pond, an inflow control system
is important. When streams are used as a water supply, the stream should
be diverted around the pond and an inlet pipe, which can be screened or
closed as needed, should be installed. When surface runoff waters are used
as a water supply, an embankment or diversion ditch with an inlet pipe,
which can be screened or closed, is recommended. Inflow-outflow control
structures designed into new ponds or installed in old ponds will prevent
and help control common farm pond problems.
Pond Size
Good sportfishing ponds should be 1 acre in size or larger. Small ponds
less than 1/2 acre in size generally do not provide enough natural food
or cover to support healthy sportfish populations and are easily overharvested.
Except for this lower size limitation, selection of pond size is left to
the discretion of the pond owner. Some advantages of small ponds (1/2 to
2 acres in size) are that they (1) can be drained and filled rapidly, (2)
are easier to treat for waterweeds and fish disease problems, and (3) are
less susceptible to bank erosion by strong winds and water currents. On
the other hand, larger ponds (2-10 acres) (1) are less subject to drought,
(2) cheaper to construct per unit of water, (3) provide more uses (irrigation,
livestock, fish farming), and (4) can support greater sportfish populations
than smaller ponds.
Pond Depth
Pond depth depends primarily on the prevailing weather conditions.
In northern states, ponds must be deeper than those in the southern United
States in order to avoid “winterkills” (fish kills caused by suffocation
under snow-covered surface ice). Similarly, ponds located in the mountains
of Virginia that develop ice cover during the winter months should be built
deeper (10 to 12 feet) than those in eastern or central Virginia (8 to
10 feet deep). Shallow ponds (less than 8 feet in depth) are not recommended,
since they may develop weed problems or get too warm during the summer
months. Deep ponds (greater than 15 feet in depth) are not recommended
because deeper waters are often devoid of oxygen and contribute little
to fish production. However, ponds used for crop irrigation, livestock
watering, and other high consumptive water uses should be deeper than 12
feet. Deep water along the shoreline discourages water weed growth. The
pond edges should be at least 3 feet deep (a 3 to 1 shoreland slope).
Water Quality
Water Temperature
Water temperature plays an important role in determing what kinds of
sportfish can survive in a particular farm pond. In general, freshwater
sportfishes can be divided into three major groups based on their temperature
preferences: coldwater fish, warmwater fish, and coolwater fish. All trout
(brook, rainbow, and brown) are coldwater fish. Coldwater fish thrive in
coldwater ponds (fed by springs or groundwater) where the average surface
water temperature for trout is below 70?F (21?C) during the summer. Optimal
water temperature for trout is about 60? to 68?F. Trout may survive at
slightly higher water temperatures, but only for short periods of time.
Water temperatures above 70?F cause stress in trout, and death occurs within
minutes at temperatures above 80?F. Warmwater fish (largemouth bass, bluegill,
sunfish and catfish), on the other hand, can survive at water temperatures
of 90?F (32?C) or higher. Most farm ponds in Virginia, particularly those
fed by surface waters, are warmwater ponds (surface water temperatures
above 75?F or 21?C during the summer) and should be stocked with warmwater
fish. Coolwater fish (smallmouth bass, rockbass, and pike) prefer an intermediate
temperature range (70? to 80?F). Coldwater ponds should be stocked with
trout and warmwater ponds should be stocked with bass, sunfish, or catfish.
Stocking farm ponds with the wrong species of fish will result in fish
kills or slow growth.
Acid or Alkaline Waters
The pH of pond water is a chemical measurement indicating how acidic
or alkaline (basic) the water is on a standard scale ranging from 0 to
14. Pure (neutral) water is neither acidic nor basic and has a pH value
of 7.0. Acid waters have pH values ranging from 0 (very acidic) to 6.9
(slightly acidic). Alkaline waters have pH values ranging from 7.1 (slightly
alkaline) to 14.0 (very alkaline). Sportfish favor waters within a range
of 6.5 to 9.0. Values above and below this range may kill fish or lower
production. Extremely acid waters (below pH 4) or alkaline waters (above
pH 11) are lethal to most sportfish. Moderately acidic or alkaline waters
may result in slow growth or low survival.
If pond waters are consistently too acidic (below pH 6), liming materials
can be broadcast over the bottoms of empty ponds or over the surface waters.
Common liming materials are agricultural limestone [CaCO3 or CaMg(CO3)
2], hydrated or slaked lime [Ca(OH)2], and unslaked or quicklime [CaO].
Finely crushed agricultural limestone is the best liming material to use
in ponds since the other liming materials may elevate the pH too high and
cause fish kills. Acidic pond waters can be treated by applying 1000 pounds
of finely ground agricultural limestone per surface acre of water each
week until a pH level near 6.5 is reached. A number of materials, including
filter alum (aluminum sulfate) and agricultural gypsum (calcium sulfate),
have been used to treat highly alkaline waters (above pH 10), but the effectiveness
of these chemicals in reducing high pH values remains questionable.
Dissolved Oxygen
Dissolved oxygen is one of the most important water quality factors
to consider in managing sportfish ponds. Without an adequate supply of
dissolved oxygen, fish cannot survive. Most of the dissolved oxygen (70
to 90%) in pond water is produced by green plants (algae and rooted water
plants) through the process of photosynthesis. Photosynthesis and oxygen
production by water plants is regulated by sunlight. On sunny days plants
produce oxygen. At night no oxygen is produced. Maximum oxygen production
generally occurs in late afternoon (2-4 p.m.) each day and during the summer
months when more sunlight is available. Minimum oxygen production generally
occurs just before dawn (sunrise) and during the winter months when less
sunlight is available. At night or on cloudy days, respiration (oxygen
consumption) by plants and fish may exceed photosynthesis (oxygen production)
during the day, resulting in critically low oxygen levels and fish kills.
Since water plants produce oxygen, a limited number growing in the pond
are beneficial. However, large growths of rooted water weeds or floating
mats of algae are harmful because they can use all the dissolved oxygen
in the pond during the night.
Pond waters should contain at least 5 mg/L (parts per million) of dissolved
oxygen to sustain a healthy population of warmwater sportfish and a minimum
of 6 mg/L for coldwater sportfish (trout). Dissolved oxygen levels below
5 mg/L stress fish resulting in low production and slow growth. Oxygen
levels below 3 mg/L for long periods of time may kill fish directly or
lower their resistance to diseases and parasites.
Muddy Waters
Muddy water is not only unattractive, but harmful to aquatic life.
High levels of suspended sediments (1) limit light penetration and oxygen
production by aquatic plants; (2) increase water temperatures; (3) smother
fish eggs; (4) suffocate bottom- dwelling fish food animals; (5) retard
the growth of sportfish; and (6) reduce the holding capacity of ponds.
Although high sediment loads seldom kill sportfish directly, muddy waters
can seriously reduce fish production. All other things being equal, clear
water ponds can produce several times more fish than muddy ponds. Turbid
water not only reduces the amount of fish food available, but seriously
interferes with the ability of sportfish to see and catch prey (most sportfish
are visual feeders). It is a sad irony that the same soil that is vital
for food production and life on land becomes a major pollutant when suspended
in waters.
Muddy pond waters are normally the result of soil erosion. Heavy rains and strong winds transport eroded soil particles into ponds from overgrazed pastures, unprotected croplands, and unvegetated shorelines. Any area where cover plants have been stripped and the bare soil is exposed provides a source of polluting sediments. Livestock trampling shorelines and wading in ponds or upstream waters add large quantities of soil sediments. Bottom feeding fish, particularly carp and bullheads, contribute to the problem by rooting and stirring up silt in their search for food.
The best way to keep pond water clear is to keep the soil on the land. Water clarity can be conserved by (1) strip cropping and contour plowing, (2) land grading and terracing, (3) installing sediment basins and soil traps at the pond inlet, (4) routing muddy water around the pond through diversion ditches, (5) planting cover crops and protecting existing shelter belts along shorelines, and (6) fencing livestock from ponds and inflowing streams. It is much easier to limit soil erosion and prevent surface runoff than it is to remove sediments once they have entered the pond.
Surface application of certain chemicals that bind and precipitate clay
particles can be used to clear muddy ponds. Chemical treatments effective
in treating muddy ponds include: (1) filter alum (hydrated aluminum sulfate,
Al2(SO4)3 • 14H2O) applied at a rate of 5 lbs./surface acre; (2) finely
ground agricultural limestone (CaCO3) applied at a rate of 500 lbs./surface
acre, and (3) agricultural gypsum (hydrated calcium sulfate, CaSO4 • 2H2O)
applied at a rate of 500 lbs./surface acre. Since the exact application
rate varies, concentrations for individual ponds should be determined by
treating pond water samples in jars and selecting the minimum level that
will cause the clay particles to precipitate within an hour. Cautious application
is advised because these chemicals can be harmful to fish life. Alum, for
example, reduces the pH and should not be used in soft water ponds with
low pH values. Chemical clearing agents provide only temporary relief;
the source of the eroded sediments and clay particles should be eliminated
by proper land management practices.
Leaking Ponds
One of the most common farm pond problems is heavy water loss through
leakage. The ability of the pond to retain water depends largely on the
characteristics of the soil at the pond site. Most leaky pond problems
can and should be prevented by cautious site selection. Before building
a pond, be sure to test the capacity of the soil to hold water. Soils with
a high clay content will minimize seepage since clay particles tend to
swell when wet and, thereby, provide a good bottom seal.
Bottom Seals
Although it is usually expensive, leaky ponds can be sealed using one
or more of a variety of compounds. The most commonly used pond sealant
is bentonite clay. Bentonite is most effective on sandy soils that contain
insufficient amounts of clay. This clay has the capacity to expand up to
20 times its original size when moistened. For best results, bentonite
should be spread evenly over the dry pond bottom at a rate of 50 lbs/100
ft (20,000 lbs/acre) mixed with the existing soil, moistened, and then
compacted with a roller. Other sealants, including soluble salts and polyphosphate
chemicals, are effective on certain soils. Laboratory analysis of the soil
is essential to determine the appropriate type of sealant and its rate
of application. Another increasingly popular method of pond sealing involves
lining the bottom with a flexible plastic or rubber sheeting of polyethylene,
vinyl, or butyl at least 2 mm thick. To protect against punctures and tears,
the pond liners should be covered by at least 6 inches of sand or fine
soil. Plastic or rubber sheeting can be purchased from local hardware stores.
Burrowing Animals
Leaking ponds may be caused by burrowing animals such as crayfish,
muskrats, and beaver, who construct their homes or “burrows” by digging
into soil banks along the shorelines of waterbodies. Tunnels dug above
the water level can decrease structural support of the embankment and increase
the risk of washout during flood conditions. These hazards are multiplied
in waters where burrowing animals are abundant and where water levels fluctuate.
Rising and falling water levels often stimulate these animals to dig new
burrows, increasing the potential for structural damage and water leaks.
If large numbers of burrowing animals and extensive tunneling activity
are undermining the structural integrity of the dam, several control measures
can be effectively employed. Efforts at total eradication are usually futile
since burrowers from upstream waters or nearby ponds can migrate considerable
distances and will continually reinvade the pond. Therefore, the control
measures suggested below should be viewed simply as actions the pond owner
can incorporate to reduce excessive numbers of crayfish or muskrats to
a level at which structural damage and water leaks will be minimized.
Crayfish
Trapping crayfish is an effective method for control. Several types
of trap are available from sporting goods outlets or can be made at home
using 1/2-inch mesh chicken wire. Modified funnel-end commercial minnow
traps are often used. The funnel openings should be enlarged to about 2
inches in diameter to allow for easy entry by large crayfish if this type
of trap is used. Lift traps, similar to the ones used to catch saltwater
crabs, are commonly used to catch crayfish. Simply lower the baited trap
to the borrom, then quickly pull it up at frequent intervals. Meat scraps,
fish heads, soybean cake, perforated cans of dog food, or almost any high-protein
substance can be used as crayfish bait. For overnight or long trap setting
times, you can enclose the bait in hardware cloth to prevent the trapped
crayfish from eating all the bait.
The habits of crayfish strongly influence how easily they are caught. Crayfish overwinter in their burrows in the bottom muds or shoreline banks, emerging as the water warms. The opening of trout season roughly corresponds with the time when crayfish first become active in Virginia. The optimal water temperature range for crayfish is between 40?F (4?C) and 75?F (24?C). If temperatures are below or above this range, crayfish become inactive and quit feeding. Crayfish are nocturnal (active at night). Traps should therefore be set in late afternoon and left overnight.
An excellent method for preventing high numbers of crayfish is to stock
and maintain a balanced population of fish. Trout, bass, catfish, and large
bluegills (bream) are all predators of crayfish and reduce excess numbers.
Other natural predators that feed heavily on both young and adult crayfish
are: amphibians (bullfrogs, salamanders), reptiles (turtles, water snakes),
waterbirds (herons, kingfishers, ducks, geese), and mammals (raccoons,
otters, mink). These beneficial creatures should be protected and encouraged
to live in or near your ponds. Natural predators, which act as biological
controls, have the advantage of providing year-round protection from burrowing
crayfish problems without the need for trapping.
Muskrats and Beaver
Muskrats and beaver can be discouraged from living in a pond by eliminating
water plants and shoreline vegetation that provide food and cover for these
burrowers. Muskrats prefer to feed on starchy aquatic plants, particularly
cattails, bulrushes, reeds, arrowhead, and aquatic grasses. Controlling
the growth of these water plants and keeping the pond banks well mowed
will limit muskrat populations. Physical barriers to prevent muskrats from
tunneling into shorelines and earthen dams can be used to reduce tunneling.
Lining the inner face of the dam with pea gravel, sand, rock rip-rap, concrete,
cement board, or wire screening (1-inch mesh) will effectively discourage
digging. These physical barriers should extend from 1 foot above the high
water mark to at least 4 feet below the normal water level.
Trapping is the most practical method for controlling muskrats and beaver.
They can be “live-trapped” with wire cage or box traps, or humanely killed
using the steel traps set underwater. Traps should be set in runways, or
den openings. If possible, trapping should be conducted during the winter
when the fur is prime. Muskrats and beaver are valuable furbearers that
represent a potential cash crop to the pond owner.
Nuisance Fish
Although many different types of freshwater fish will live in Virginia
ponds, only a few fish species will produce good sportfishing over many
years. The fish species recommended for stocking warmwater ponds in Virginia
are largemouth bass, bluegill sunfish (bream), redear sunfish (shell crackers),
and channel catfish. A single pond can be stocked with all of these species
or desired combinations, but should contain no other types of fish. Coldwater
ponds should contain only trout. All other types of fish, particularly
crappie, bullheads, carp, goldfish, perch, suckers, and other types of
sunfish will compete with desirable fish for food, cover, and spawning
sites. Nuisance fish tend to overpopulate ponds and ruin sportfishing.
Moreover, nuisance species and wild fish obtained from nearby streams or
ponds often carry diseases or parasites that infect sportfish and reduce
fishing quality.
Three major causes for nuisance fish problems are (1) failure to kill all fish life in a pond and its inflowing waters before hatchery fish are stocked, (2) failure to prevent the entry of wild fish into a stocked pond, and (3) failure to stock only the recommended fish species. Before stocking, fish life can be eliminated by completely draining and drying the pond bottom or by partially draining and applying fish poison to the remaining waters. Inflowing waters should also be screened or filtered to keep out unwanted fish. A saran screen filter (100 meshes per inch) can be used to filter out nuisance fish and their eggs. The best way to stock only the recommended types of fish is to obtain all stocks from a commercial hatchery. Reliable commercial hatcheries will not only provide the proper kinds of sportfish in the correct numbers and sizes, but will also guarantee live delivery of disease-free fish. This is a particularly valuable service since small fish are very difficult to identify. Unless one is an expert at fish identification and diseases, never stock fish from nearby streams, ponds, or lakes. The pond owner must also ask neighbors and friends not to introduce any fish into the pond.
Desirable Sportfish Nuisance Fish
Largemouth Bass Black Crappie (Speckled Perch)
Bluegill Sunfish (Bream) White Crappie (Silver Perch)
Redear Sunfish (Shell Crackers) Yellow Perch
Channel Catfish Carp
Brook Trout Goldfish
brown Trout Suckers
Rainbow Trout Bullheads (Mudcats)
Pumpkinseed Sunfish
Green Sunfish
Golden Shiners
Minnows
Fish Diseases and Parasites
Fish are continuously exposed to a wide variety of diseases and parasites.
Fish are subject to infection by disease-causing viruses, bacteria, and
fungi. Fish are also parasitized by tapeworms, leeches, grubs, and lice.
All of these organisms normally occur at low levels in most farm ponds
and in limited numbers on many fish. Fish disease-causing organisms and
parasites seldom cause problems in farm ponds. A few parasitized fish in
a farm pond are not unusual. However, large numbers of infected fish are
cause for concern since slow growth, sterility, and fish kills may result
from extensive diseases and parasite infestations.
Fish diseases and parasites seldom reach epidemic levels. Sudden, large fish kills in farm ponds are rarely caused by diseases or parasites. Fish suffering from diseases or parasites usually die slowly—a few fish each day. Only in severe cases when fish are in poor condition, starving, crowded, injured, mixed with wild fish, or stressed by rough handling, low oxygen levels, high temperatures or chemical toxins, do diseases and parasites become a serious problem. Fish suffering from disease or parasite infections are easily recognized. Some of the early warning symptoms are: (1) a general loss of appetite or refusal to feed; (2) abnormal coloration and the erosion of the scales or skin; (3) abnormal distribution such as crowding at the surface, near inflowing waters, or in the shallow water at the sides of the pond; (4) abnormal activity such as flashing, twisting, whirling, or lack of activity. Fish exhibiting any unusual form of behavior should be closely examined for external symptoms of disease or parasites. Infected fish usually show visible sores, discoloration, bleeding, swollen areas, tumors, popeyes, small black or white spots, or other abnormal growths on the head, body, and fins.
There are few practical methods for treating diseased or parasitized
fish in natural pond, lake, or stream waters. Sick fish can be effectively
treated in hatcheries and aquariums under controlled conditions. However,
in natural waters it is almost impossible to eradicate a disease or parasite
without draining, drying, and disinfecting the pond bottom soil and destroying
all the fish. Some chemicals can be used for partial treatment (see Virginia
Cooperative Extension publication 420-899), but even limited treatments
are expensive, time-consuming and seldom successful. Therefore, pond owners
should make every attempt to prevent fish diseases and parasites from becoming
a problem. Pond owners who: (1) stock only healthy fish from disease-free
commercial hatchery stocks, (2) exclude all wild fish from the pond, (3)
do not transfer fish from other ponds, lakes, or streams into the pond,
(4) follow the recommended stocking rates to avoid overcrowding and starvation,
and (5) prevent fertilizer or pesticide runoff from entering the pond,
seldom experience fish disease or parasite problems.
Aquatic Animals
Water Snakes
Although water snakes do eat some fish, they pose no serious threat
to pond fish populations or man. Water snakes are not poisonous! Of the
36 different types of snake found in Virginia, only two species, the northern
water snake (Natrix sipedon) and the brown water snake (Natrix taxispilota),
are true water snakes. Many people confuse these water snakes with the
eastern cottonmouth or water moccasin (Agkistrodon piscivorus) which is
a poisonous, water-dwelling snake. However, the cottonmouth is found only
in the extreme corner of southeastern Virginia, near the Dismal Swamp.
Since these snakes have never been found further west than Petersburg,
about 90% of the state has no cottonmouths. Water snakes will bite if handled,
but are relatively harmless and should not be indiscriminately destroyed.
Clearing debris and mowing vegetation at the pond edges reduces hiding
places for snakes and will effectively reduce their numbers.
Turtles
Turtles are beneficial scavengers that feed primarily on aquatic plants
and dying fish. Turtles are not harmful to fish populations and can actually
improve fishing by removing unhealthy fish. Of the 18 species of turtle
found in Virginia, only the snapping turtle can become a nuisance by occasionally
stealing fish bait or eating ducklings. Turtles seldom cause problems and
should not be indiscriminately killed. Snapping turtles can be caught with
trot lines, large minnow-type traps, rat traps, or box traps baited with
fish heads, fresh meat, or watermelon rind. Snapping turtle meat is considered
a delicacy if properly prepared.
Water Birds
A wide variety of wading birds (sandpipers, terns, herons), waterfowl
(grebes, mergansers, ducks, geese), and other birds (kingfishers, gulls,
and ospreys) feed on water animals and are attracted to ponds. These birds
do eat some fish, but rarely can catch enough fish to seriously affect
sportfish populations. These birds, like turtles and water snakes, are
beneficial predators that cull weak and diseased fish from ponds. Wading
birds like the greater yellowleg sandpiper provide a very useful service
to the pond owner by consuming thousands of insect pests. They are very
effective in controlling mosquitoes, biting flies, leeches, snails, and
other nuisance animals that dwell along the shorelands of ponds. Moreover,
these birds contribute to the beauty and scenic enjoyment of pond owners.
Many of these birds are becoming rare and nearly all are protected by state
or federal laws. They should not be killed or discouraged from feeding
or nesting on ponds. Pond owners who are fortunate enough to have these
species on their property should enjoy and protect them so that their children
may have similar pleasures.
Waterfowl
Wild ducks and geese cause few farm pond problems. In fact, many pond
owners wish to attract nesting and migrating waterfowl. The most critical
decisions for a pond owner desiring waterfowl concern siting and design
of the pond. Guidelines for creating ponds attractive to waterfowl differ
from those for ponds used for most other common purposes. The ideal sportfish
pond, with its regular shape, steep banks, limited weed growths, and deep
water, is not best for attracting ducks. Waterfowl prefer to feed and raise
their young in weedy, shallow ponds located away from human activity. It
is usually not worthwhile to artificially seed a shallow pond in Virginia,
since naturally occurring aquatic plants produce good food and cover. However,
it is wise to construct nesting islands located at least 10 yards from
the banks, to provide nesting habitat for mallard and black ducks and Canada
geese. Wood ducks can be attracted to ponds by placing nest boxes on poles
or in nearby trees.
Livestock
Domestic livestock (cattle, horses, hogs) should be completely fenced
out of ponds used for sportfish production. Water pollution from livestock
wastes and soil erosion caused by the trampling/grazing activities of livestock
at pond edges or in upstream waters can seriously reduce the growth and
production of sportfish. Livestock wastes and eroded soil particles entering
pond waters create a number of problems including (1) infilling of the
pond basin; (2) reduction of storage capacity and depth; (3) reduction
of water clarity and light penetration; (4) increasing water temperatures;
(5) low dissolved oxygen levels; (6) smothering of fish eggs and fish food
animals; (7) stimulating algae and weed growths; and (8) fish kills. To
protect pond water quality, water for livestock should be piped by gravity-flow
into watering troughs located below the dam, downstream from the pond.
Drainage from barnyards, feeding lots, bedding areas, or other sources
of contamination should be diverted around the pond. If fencing the entire
pond is not practical, pave livestock trails to the pond with gravel and
confine livestock to a small area of the pond by partial fencing.
Aquatic Weed Control
Although limited numbers of aquatic plants growing in ponds are beneficial,
dense growths of algae and other waterweeds can seriously interfere with
man's uses of ponds and create undesirable changes that threaten pond life.
Nuisance growths of waterweeds may restrict swimming, boating, fishing,
and other water sports in recreational ponds. Certain types of waterweeds
impart unpleasant taste, emit offensive odors, and discolor pond waters.
In valuable sportfish ponds, dense growths of aquatic vegetation provide
cover for small fish, permitting overpopulation and stunted fish populations.
Decomposition of waterweeds depletes dissolved oxygen, often resulting
in the suffocation of sportfish (winter kills and summer kills).
There are a number of recommended methods for controlling waterweeds
in ponds. Selecting the best technique or combination of techniques depends
on the kind of nuisance weed present, the extent of the problem, the nature
of the problem, economic considerations, and local environmental conditions.
To obtain successful results, control measures should be carefully selected.
For additional help in controlling waterweeds, consult your county Extension
or Soil Conservation agent (see Virginia Cooperative Extension Publication
390-809).
Watershed Management
A major objective in waterweed control is to keep the soil and its
nutrients on the land and out of pond waters. Land use practices that prevent
soil erosion and limit the movement of soil particles into ponds are essential
in controlling waterweed growth. Eroded soil sediments not only fill in
ponds, but also transport nutrients which stimulate weed growth. Wise land
use practices are fundamental in controlling waterweeds. These include:
(1) no-till farming, (2) strip cropping, (3) contour plowing, (4) installing
sediment basins, (5) preventing livestock overgrazing, (6) fencing livestock
out of ponds and inflowing streams, and (7) creating shelterbelts along
shorelines. All of these practices can significantly reduce waterweed problems.
Careful consideration should be given to preventing animal wastes and fertilizers
from entering pond water. Feed lot and barnyard runoff should be channeled
around a pond by using a grass-lined diversion ditch.
Dredging and Deepening
The removal of pond bottom sediments is a very effective way to control
rooted waterweeds in shallow ponds. Dredging reduces waterweed problems
directly by removing the weeds, bottom sediments, and their associated
nutrients. Dredging and deepening shallow shoreline areas limits weed growth
indirectly by exposing a soil layer that may be nutrient-poor or impervious
to plant roots and by decreasing the amount of sunlight available to plant
life. Dredging can be conducted on dry land, after the pond has been drained,
or underwater. Underwater or hydraulic dredging is normally too expensive
for use in small ponds. On drained pond bottoms, dry-land excavation machinery
such as bulldozers or draglines can be used. Although digging and removing
bottom sediments by hand is hard work, it represents a simple, economical,
and efficient alternative to mechanical dredging. The dredge spoils must
be trucked away from the pond basin to prevent subsequent contamination.
Harvesting
The physical removal of waterweeds from ponds is an ideal control technique.
Waterweed harvesting consists of three essential steps. These are (1) cutting
or uprooting the weeds, (2) collecting the cut weeds, and (3) removing
the weeds from the pond. Harvesting can be accomplished by simple hand
tools and physical labor or with the help of cutting machines. In shallow
shoreline areas, weeds can be pulled by hand, cut by sickle, dug out with
a hoe, and removed from the water with rakes or forks. In large ponds,
a variety of commercial powered cutting machines are available. Some cutting
blades can be mounted on the bow of a motor boat. The success of any harvesting
operation depends on the prompt and complete removal of all cut weeds.
Haphazard or partial removal of the cut weeds can increase the problem,
since each unremoved weed fragment has the potential to form a new weed.
Also, cut weeds left in the water will decay and release nutrients that
stimulate future weed growths. Decomposing weeds left in the pond use oxygen
and can cause fish kills. Harvesting provides immediate relief from nuisance
weed growths and does not endanger fish life.
Water Level Management
Lowering the water level of a pond can be an easy way to control nuisance
waterweeds. Pond drawdown, particularly during the winter months, exposes
weeds to harsh conditions including freezing, dessication (drying out),
strong wind action, and bottom sediment compaction. In addition, frost
heaving of the bottom sediments uproots the weeds and aids in their destruction.
To insure effective over-winter control, the bottom muds should freeze
to a depth of 4 inches for several weeks or longer. Freezing weather conditions,
however, are not necessary for successful weed control. Pond drawdown at
any time of the year will reduce waterweed growth. Waterweeds exposed by
lowering the water level must be collected and removed from the pond basin,
or the rotting weeds will contribute nutrients that promote new weed growths
when the water level is once again raised. In ponds without drains, water
pumps can be used to manage the water levels.
Shading
Limiting the amount of sunlight available to aquatic plants by floating
black plastic sheeting on the water surface or by using dark-colored dyes
has been effective in controlling waterweeds. Black plastic sheeting attached
to styrofoam floats serves as a floating shade which can be moved easily
from one place to another for spot treatment of nuisance water plants in
small areas. This technique is ideal for weed control around boat docks,
fishing piers, and swimming beaches. Several commercially available water
dyes, including nigrosine, analine, and aqua-shade, can be used to color
the water in order to reduce light penetration and shade out nuisance plants.
To be effective, the dyes must persist or the floating black plastic raft
should remain in one place for four weeks or longer. For the best results,
this technique should be used in early spring at the start of the growing
season before the waterweeds have had a chance to establish themselves.
Pond Bottom Linings
Covering the bottom sediments of small ponds with either plastic sheeting,
a layer of mineral soils (sand, gravel, clay) or both of these materials
is an effective waterweed control technique. Perforated black plastic sheeting
covered with a blanket of sand or gravel provides a relatively cheap alternative
to dredging. These coverings limit the exchange of nutrients from the bottom
muds to aquatic plants and inhibit the establishment of rooted waterweeds.
In addition, sediment covers provide a firm stable bottom which can minimize
water loss. Plastic sheeting (4 mil or thicker) should be evenly weighted
and perforated with small holes to permit the escape of gases produced
by decomposition and prevent ballooning. If only a mineral soil blanket
is used to cover the bottom sediments, a 6- to 8-inch layer often is necessary.
Covering the pond or lake bottom sediments with a layer of sand, gravel,
or another mineral soil has proved less effective than using plastic sheeting
in combination with mineral soil. Black plastic sheeting overlaid with
several inches of mineral soil is recommended. Important wetland habitats,
such as fish spawning or waterfowl nesting areas, should not be covered.
Biological Controls
Introducing animals and plants that eat or compete with waterweeds
represents another control method. Herbivorous animals (those that eat
plants) include a wide variety of insects, snails, crayfish, tadpoles,
turtles, fish, ducks, geese, and swans which can be stocked in ponds to
consume waterweeds. The major problem with introducing herbivorous animals
into ponds for waterweed control is that their body wastes act as fertilizers
and stimulate weed growth. Herbivorous animals, by recycling nutrients,
may do more harm than good. Many different types of aquatic plant compete
with waterweeds for space, light, nutrients, and other critical factors.
Therefore, it is sometimes possible to discourage the growth of nuisance
waterweeds by planting beneficial aquatic plants. Some biological control
agents are more harmful than beneficial. Check with county agents before
introducing animals or plants into your pond. Please note that the release
of exotic (nonnative) animals or plants into Virginia without specific
authorization is strictly forbidden by state laws.
Chemical Controls
The treatment of weed-infested waters with herbicides (chemicals that
kill plants) is a method that must be used with caution and only after
careful consideration of alternative control methods and the potential
uses of the treated water for drinking, livestock watering, swimming, fish
production, irrigation, or other uses. In no instance should a herbicide
treatment be considered as a total cure for a pond weed problem. Rather,
the weed problem should be approached using a combination of the methods
listed above and, if absolutely necessary, supplemented with chemical control
agents. Caution must be taken to apply herbicides at the correct time,
at the correct rate, and in accordance with label instructions. Chemicals
that kill nuisance waterweeds may also kill beneficial water weeds and
fish, disrupt aquatic food chains, or have other undesirable side effects.
Chemical treatments are costly, generally provide only short-term relief
from the symptoms of the problem, and should not be viewed as a solution.
Realize that the basic cause of excessive water weed growth—overfertile
water—is not affected by herbicides. It is important to understand that
when waterweeds are killed by chemicals, they rot and release their contained
nutrients (fertilizers) into the pond water. These nutrients are then available
to stimulate future weed growth, often requiring more treatments. For successful,
long-term control of water weeds, a continuous program using several of
the weed control measures listed above, particularly preventing fertilizer
from entering the pond and physically removing the weeds, is recommended.
(For additional information on chemical control alternatives, consult Virginia
Cooperative Extension Publication 456-017.)
Balanced or Unbalanced Populations
The term “balance” refers to the relative numbers and sizes of predatory
fish (bass) and prey fish (bluegill) in a pond. A balanced sportfish population
is one with a satisfactory number of catchable-sized bass and bluegill.
Ponds with balanced sportfish populations provide desirable numbers of
harvestable- sized fish of both species. For example, if both fish species
are abundant and the average size of bluegills harvested is 6 inches or
larger and bass average 12 inches (1 pound) or more, then the population
is considered balanced.
In contrast, an unbalanced population is characterized by too many small fish and too few large fish of either species. In most cases, unbalanced populations are indicated by an overabundance of small bluegill (averaging 3 to 5 inches in length), and very few but some large bass (averaging 15 inches or larger). This condition usually occurs when bass are overharvested and bluegill are underharvested. However, unbalanced populations can also be indicated by an overabundance of small bass (averaging 9 to 10 inches) and an abundance of large bluegill (averaging 6 inches or larger). In either case, excessive numbers of one species or the other will rapidly exploit the available food supply, resulting in slow growth and stunted populations.
Table 1. Probable condition (balanced or unbalanced) of pond sportfish populations based on angler catch records and minnow seine hauls
Average Length Probable
Catch (Inches) Abundance Condition
I. Angler Catch
1. Situation One: Balanced
Bluegill 6" Abundant
Bass 12" Abundant
2. Situation Two: Unbalanced
Bluegill 3-5" Abundant
Bass 15" Rare
3. Situation Three: Unbalanced
Bluegill 6" Few
Bass 7-10" Abundant
II. Minnow Seine
1. Situation One: Balanced
Bluegill 0.5-2" Abundant
Bass 1-4" Few
2. Situation Two: Unbalanced
Bluegill 0.5-2" Few
Bass 1-4" Abundant
3. Situation Three: Unbalanced
Bluegill 0.5-2" Abundant
Bass 1-4" None
Pond owners can monitor the condition of their sportfish populations by (1) keeping an accurate record of numbers, sizes (length or weight), and species of all fish caught by fishing, and (2) assessing reproductive success each summer by making several hauls along the shoreline with a large minnow seine (1/2-inch mesh, 15-20 feet long) and recording the numbers, sizes, and species of young fish present. Table 1 can be used as a general guide to the probable condition of the population. For a more accurate analysis of balance, angler catch and seining catch information can be sent by your local Extension Agent to the Extension Fisheries Specialist at Virginia Tech.
A number of corrective methods can be used to control excessive numbers
of small fish and restore population balance in ponds. These include: (1)
harvestring large numbers of small fish by angling and seining with a minnow
net (20 feet or longer with a 1/2-inch mesh size); (2) destroying spawning
beds by raking over or trampling active nests; (3) stocking largemouth
bass (12 inches or larger) to supplement the predator population; (4) lowering
the water level to force small fish from shoreline cover into open water
where they are more susceptible to predation; (5) partial poisoning by
applying a fish toxicant in shallow shoreline areas; and (6) removing dense
growths of water weed which provide shelter for small fish and trap nutrients
that would otherwise be used to produce fish food organisms. All of these
methods can be used singly or in combination to reduce overcrowding without
killing the larger, more desirable sportfish. However, in ponds that are
severely overcrowded with stunted fish, the only realistic solution is
to kill all the fish by draining and poisoning and then restock the pond.
Artificial Feeding
Artificial feeding is usually unnecessary and generally not recommended
in sportfishing ponds. Most ponds in Virginia, if correctly stocked, will
provide enough natural food to support healthy sportfish populations without
supplemental feeding. Artifical feeding is a time-consuming, costly, and
potentially harmful process that often is not worth the effort, expense,
or risk. Overfeeding can create serious water quality problems. Decomposition
of uneaten food and waste products can reduce dissolved oxygen levels and
cause fish kills. Moreover, since sportfish prefer to eat live aquatic
animals (insects, crayfish, frogs, and small fish) rather than dry, pelleted
feeds, commercial feeds may not be readily consumed. Largemouth bass usually
will not accept artificial feeds.
Artificial feeding is necessary in hatcheries and commercial fish farms where fish are grown at high densities and food is limited. Since channel catfish and trout accept dry, pelleted feeds, some pond owners who raise those species as food fish prefer to use commercially prepared feeds. Pelleted catfish and trout feed is available from farm supply dealers.
If artificial feeding is attempted, pond owners should carefully follow
some important guidelines. These include: (1) do not provide more feed
than can be completely eaten in 10 minutes (food remaining after this time
is seldom eaten and pollutes the water); (2) if fish suddenly cease feeding,
stop feeding and check for low oxygen, diseases, or other problems; (3)
reduce feeding rates at high and low water temperatures (above 90?F and
below 60?F for catfish, above 67?F and below 50?F for trout); (4) do not
feed after sundown or at night when dissolved oxygen levels normally decrease;
(5) feed on a regular schedule at the same time each day; (6) use floating
pellets to allow for observation of feeding activity and general fish health;
(7) use the pellet sizes recommended for the size of the fish grown; (8)
distribute the feed evenly throughout the pond; and (9) do not substitute
other animal feeds for fish feed. Pond owners should realistically evaluate
the efforts and costs of a feeding program. Discontinuing an established
feeding program or haphazard feeding can create overcrowded conditions
and fish kills.
Fertilization
In Virginia, fertilizing pond waters to increase sportfish production
is not recommended for a number of reasons. Some major objections to applying
agricultural fertilizers directly into fish ponds include: (1) most ponds
in Virginia are naturally fertile and will usually produce good crops of
sportfish without artificial fertilization; (2) fertilization is expensive
and most pond owners do not harvest enough fish to justify the added costs
or efforts required to fertilize correctly; (3) haphazard or discontinuous
fertilization programs can create serious water quality problems and fish
kills; (4) added fertilizers may stimulate growths of nuisance algae and
water weeds rather than desirable plant life (phytoplankton); and (5) the
results of fertilizing ponds are generally unpredictable, often undesirable,
and can be harmful to aquatic life.
Probably the greatest single misconception about fish ponds is that small, stunted fish are the result of “infertile or unproductive” pond waters. This popular myth suggests that simply sprinkling fertilizer into ponds will prevent overcrowding and stunted sportfish populations. This is, of course, not true. In fact, the sizes of sportfish in a pond are largely determined by the ratio of predatory fish to prey fish—what is called “balance.” Good growth of sportfish depends on the presence of large predatory fish which reduce the abundance of small fish, leaving more food for the survivors. Without an abundance of predatory fish, fertilization will only increase the problem by sustaining more small fish to compete with one another. To make matters worse, the dense weedbeds often produced by fertilization provide cover for small fish so that large predatory fish cannot prey on them effectively. Contrary to popular belief, fertilization will not prevent or cure overcrowding.
After considering the potential problem, a pond owner may wish to initiate
a pond fertilization program, particularly if natural fertility is low
and large numbers of fish are to be harvested. Applications of a complete
fertilizer (8-8-2 ratio) at a rate of 100 pounds per surface acre should
begin in early March and be followed by a second application in two or
three weeks. The fertilizer should promote a phytoplankton “bloom,” characterized
by green water. For the remainder of the year, applications should be made
at monthly intervals or whenever a hand submerged underwater to a depth
of about 18 inches becomes visible. Fertilization should be discontinued
at the end of the growing season (October) and resume each March. If a
fertilizer program cannot be maintained, do not fertilize. Discontinuous
or haphazard applications of fertilizer will cause more harm than good.
Suggested Readings
Virginia Cooperative Extension Publications:
“Stocking Sportfish in Virginia Ponds: Methods and Commercial Supply Sources.” Publication 420-009.
“Pond Construction: Some Practical Considerations.” Publication 420-011.
“Treating Fish Disease and Parasite Problems.” Publication 420-899.
“Planning for Commercial Aquaculture.” Publication 420-012.
“Catfish Farming in Cages in Virginia Ponds and Lakes.” Publication
420-918.
Books:
Management of Lakes and Ponds. G. W. Bennett: Van Nostrand Reinhold
Co., 450 W. 33rd St., New York, NY 10001. $15.95.
Sources of Assistance for Farm Pond Problems
Virginia Cooperative Extension
Contact your Extension agent
Virginia Tech
Fisheries Extension Specialist
Department of Fisheries and Wildlife
152 Cheatham Hall
Blacksburg, VA 24061
(540) 231-5059
Virginia Commission of Game and Inland Fisheries
Contact your District Fish Biologist.
Fish Division
PO Box 11104
Richmond, VA 23230
(804) 257-1000
Characteristics of a Good Sportfish Pond
1. Topography Above the flood plain
2. Water supply Groundwater or surface water
3. Water quantity Adequate to keep the pond filled
4. Water level Stable, relatively constant
5. Bottom soil type High clay content
6. Inflow waters Screened or filtered
7. Drain type Sufficient size
8. Shoreland slope Steep, 3 to 1 slope
9. Pond depth 8 feet or more
10. Pond size 1/2-acre or more
11. Pond edges grass, well vegetated
12. Temperature warmwater (> 70?F); coldwater (<70?F)
13. pH 6.5 to 9.0 range
14. Dissolved oxygen 5 mg/L or more
15. Turbidity l ow color and silt load
16. Fertility natural
17. Wild fish eliminated
18. Stocking hatchery fish